3b fuel system and carburation

90-831996R1 JUNE 1996 3B-–1FUEL SYSTEM

B

FUEL SYSTEM &CARBURETION

FUEL PUMPRECIRCULATION SYSTEMREED VALVE ASSEMBLYAUTO ENRICHNER

3

3B-0 90-831996R1 JUNE 1996FUEL SYSTEM

Table Of ContentsPage Page

Fuel Pumps 3B-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . General Information 3B-1. . . . . . . . . . . . . . . . . . .

Special Tools 3B-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . Removing/Disassembling

Fuel Pump 3B-2. . . . . . . . . . . . . . . . . . . . . . . . . . . Assembling and Installing Fuel Pump. 3B-3. . . . . . Fuel Pump Exploded View 3B-5. . . . . . . . . . . . . . . . Fuel Recirculation System 3B-6. . . . . . . . . . . . . . . . .

System Description 3B-6. . . . . . . . . . . . . . . . . . . Testing Fuel Recirculation System 3B-6. . . . . .

Fuel Recirculation System 90/95 HP 3B-6. . . . . . . . Fuel Recirculation System 1995 120 HP 3B-7. . . . Fuel Recirculation System 1996 120 HP 3B-8. . . . Reed Valve Assembly 3B-9. . . . . . . . . . . . . . . . . . . .

Removing and InspectingReed Valve Assembly 3B-9. . . . . . . . . . . . . .

Inspecting and InstallingReed Block Assembly 3B-9. . . . . . . . . . . . . .

Reed Plate, Intake Manifoldand Auto Enrichner - 90/95 HP 3B-10. . . . . . . .

Reed Plate, Adaptor Plate andAuto Enrichner - 120 HP 3B-12. . . . . . . . . . . . . .

Auto Enrichner 3B-14. . . . . . . . . . . . . . . . . . . . . . . . . . System Description 3B-14. . . . . . . . . . . . . . . . . . Testing Auto Enrichner 3B-14. . . . . . . . . . . . . . .

90-831996R1 JUNE 1996 3B-1FUEL SYSTEM

DANGERFIRE AND EXPLOSION HAZARD. Observe fireprevention rules, particularly NO SMOKING.Before servicing any part of the fuel system,disconnect electrical system at the battery. Drainthe fuel system completely. Use an approvedcontainer to collect and store fuel. Wipe up anyspillage immediately. Materials used to containspillage must be disposed of in an approvedreceptacle. Any fuel system service must beperformed in a well ventilated area.

FUEL LEAKAGE FROM ANY PART OF THE FUELSYSTEM CAN BE A FIRE AND EXPLOSIONHAZARD WHICH CAN CAUSE SERIOUS BODILYINJURY OR DEATH. Careful periodic inspection ofthe entire fuel system is mandatory, particularlyafter engine storage. All fuel components,including fuel tanks, whether plastic, metal, orfiberglass, fuel lines, primer bulbs, fittings,swelling, and must be inspected for corrosion.Any sign of leakage or deterioration necessitatesreplacement before further engine operation.

Fuel PumpsGeneral Information

Fuel Pump Description/OperationThe fuel pump is a crankcase-pressure-operated, di-aphragm-type pump. Crankcase pulsating pressureis transferred by way of a passage (hole) from thecrankcase to the fuel pump.

When the piston travels upward a vacuum is createdin the crankcase. This vacuum pulls in the fuel pumpdiaphragm, the inlet check valve (in fuel pump) isopened fuel is drawn into fuel pump.

Downward motion of the piston forces out the fuelpump diaphragm, closes the inlet check valve (tokeep fuel from returning to fuel tank) and opens theoutlet check valve, forcing fuel to the carburetors.

Checking for Restricted Fuel FlowCaused by Anti-Siphon ValvesWhile anti-siphon valves are helpful from a safetystand-point they clog, may be too small, or they mayhave too heavy a spring. The pressure drop that oc-curs with these valves can create operational prob-lems and/or powerhead damage by restricting flow offuel. Some symptoms of restricted (lean) fuel flow are:1-Loss of fuel pump pressure2-Loss of power3-High speed surging4-Preignition/detonation (piston dome erosion)5-Engine hesitates upon acceleration6-Engine runs rough7-Engine quits and cannot be restarted8-Engine will not start9-Vapor lock

Any type of anti-siphon device must be located be-tween the engine fuel inlet and fuel tank outlet. Amethod of checking [if such a device (or bad fuel) isa problem source] is to operate the engine with a sep-arate fuel supply which is known to be good.

If it is found that the anti-siphon valve is the cause ofthe problem, either 1) replace the anti-siphon valve,or 2) replace it with a solenoid-operated fuel shutoffvalve.

TestingInstall clear fuel hose(s) between fuel pump and car-buretor(s). Run engine, and inspect hose(s) for airbubbles. If air bubbles are found, see “Air Bubbles inFuel Line” . If air bubbles are NOT found, see “Lackof Fuel Pump Pressure”.


Troubleshooting Fuel Pump

PROBLEM: Air Bubbles in Fuel Line

Possible Cause Corrective Action

Low fuel in tank. Fill tank.

Loose fuel line connec-tion.

Inspect and tighten con-nections.

Fuel pump fitting loose. Tighten fitting.

A hole or cut in fuel line. Inspect condition of fuellines and replace anyfound bad.

Fuel pump anchorscrews loose.

Inspect and tighten allscrews.

Fuel pump gasketsworn out.

Rebuild fuel pump.

PROBLEM: Lack of Fuel Pump Pressure

Possible Cause Corrective Action

Anti-siphon valve. Refer to “Checking forRestricted Fuel FlowCaused by Anti-siphonValves” preceding.

Air in fuel line. “Air Bubbles in FuelLine” preceding.

Dirty or clogged fuel fil-ter.

Clean or replace filter.

Dirty or clogged fuelpickup in fuel tank.

Clean or replace pickup.

Worn out fuel pump dia-phragm.

Rebuild pump.

Defective check valvesin fuel pump.

Rebuild pump.

Pulse hole plugged. Remove fuel pump andand clean out hole.

Diaphragm gasket dis-torted or out of place.

Align or replace gasketas necessary.

Special ToolsDescription Part Number

Hose Clamp Pliers FT-8900

RTV Sealant 92-90113--2

Removing/DisassemblingFuel Pump1. Loosen screw on sediment bowl.

2. Remove bowl from pump body.

a

a - Screw

3. Remove gasket and screen.

a

b

a - Gasketb - Screen


4. Remove and disassemble fuel pump fitting,screws and washer, nuts, fuel pump body, boosterspring retainer, booster spring, diaphragm, gas-ket, spacer, and spacer plate gasket.

a

b

c

d

e

g

hi j

f

a - Fuel Pump Fittingb - Screw and Washerc - Nutd - Fuel Pump Bodye - Booster Spring Retainer

f - Booster Springg - Diaphragmh - Gasketi - Spacerj - Spacer Plate Gasket

5. Test fuel check valves by lightly pressing on plasticseats.

� Be sure check valve seats when tension is re-leased.

6. Replace fuel pump check valves as necessary.

a

bc

d

ea - Center Check Valve

b - Second Stage CheckValve

c - Gasketd - Screwse - First Stage Check Valve

NOTE: Removal of the second stage check valvemay cause permanent damage to the pump body,therefore, if replacement is necessary it may be nec-essary to replace the pump body.

7. Replace bowl gasket, fuel pump body gasket, andcenter check valve gasket.

IMPORTANT: Replace all worn and/or damagedparts.

Assembling and InstallingFuel Pump1. Install booster spring and retainer.

a

b

a - Springb - Retainer

2. Position diaphragm and gasket on pump body.


3. Compress spring using a putty knife. Install screwsin pump body.

ba

a

a - Long Screwsb - Short Screws

4. Install spacer plate, nuts and gasket.

ab

c

a - Spacer Plateb - Nutsc - Gasket

5. Position fuel pump assembly on transfer port cov-er. Tighten screws securely.

� Apply sealant (p/n 92-90113--2) to threads of fit-ting. Install fitting.

a

a - Fitting

6. Install fuel hoses.

a

b

c

a - Fuel Outlet Hoseb - Fuel Inlet Hose Connected to Sediment Bowlc - Pulse Hose

7. Install screen in sediment bowl. Install sedimentbowl on fuel pump.

a

a - Screen - Edge Turned Toward Engine

8. Install gasket on pump body.

a

a - Gasket, Aligned On Pump Body Keyway


IMPORTANT: Position sediment bowl with hosefitting at the 4 o’clock position.

a

a - Hose Fitting At 4 O’Clock Position

Fuel Pump Exploded View

RTV Sealant92-90113--2


Fuel Recirculation SystemSystem DescriptionAt idle, unburned fuel collects and puddles in thecrankcase behind the reed valves. The recirculationsystem is a means to route this excess, unburned fuelback to the combustion chamber.

One way check valves are located on the crankcasecover, typically below the carburetors. Crankcasepressure forces the puddled fuel through the checkvalves. A hose connected to the check valve routesthe fuel to the transfer port cover, whereby the fuel isintroduced back to the combustion chamber.

Testing Fuel Recirculation System1. Test for proper air flow through check valves as in-

dicated by arrows.

Fuel Recirculation System 90/95 HP


Fuel Recirculation System 1995 120 HP


Fuel Recirculation System 1996 & 1997 120 HP


Reed Valve AssemblyRemoving and Inspecting Reed ValveAssembly

WARNINGAlways disconnect battery and remove spar kplug leads from spark plugs before working onmotor.

1. Remove attenuator cover.

2. Remove carburetors.

SEE CARBURETOR SECTION FOR MORE INFOR-MATION

3. Remove auto enrichner.

4. Remove recirculation hose from manifold.

5. Remove bolts securing manifold assembly tocrankcase cover.

6. Remove manifold assembly from cylinder block.

7. Remove reed block assembly from reed plateadaptor.

ab

d

e

c

NOTE: 90/95 HP Shown

a - Reed Block Assemblyb - Gasketc - Reed Plate Adaptor

d - Gaskete - Manifold

Inspecting and Installing Reed BlockAssembly1. Inspect reeds for any chipping or cracking.

NOTE: The reeds are not serviceable, replace reedblock assembly if any discrepancies are found.

2. Inspect reed opening. Replace reed block assem-bly if reed is standing open more than .010” (.254mm).

a

bc

d

a - Maximum Opening .010” (.254 mm)b - Reed Stopc - Reedd - Reed Block

3. Clean all gasket surfaces.

4. Using new gaskets, install reed block assembly toreed plate adaptor.

5. Using new gasket, install manifold and reed plateassembly into cylinder block. Secure assembly tocylinder block with screws.

6. Install auto enrichner.

7. Install recirculation hose to manifold.

8. Install carburetors.

SEE CARBURETOR SECTION FOR MORE IN-FORMATION

9. Install attenuator cover.


Reed Plate, Intake Manifold and Auto Enrichner - 90/95 HP

4

56

12

78 9

1011 12

13

14 1516 17

18

13

13

13

13

19

19

20

21

22

232425

26

3


Item Qty. Description Torque

Lb. In. Lb. Ft. N·m

1 3 Reed Block Assembly

2 1 Gasket (Top)

3 2 Gasket (Center/Bottom)

4 1 Adapter, Reed Plate

5 1 Gasket, Intake Manifold

6 1 Manifold Assembly, Intake

7 8 Screw (1/4-20 x 1”)

8 6 Stud (5/16-18 x 1-1/4”) With Dri Loc

9 6 Nut (5/16-18)

10 1 Elbow

11 6 Screw (1/4-20 x 1-1/2”)

12 2 Fitting

13 6 Clamp

14 1 Hose, Molded (Top) Connect to Upper Manifold Elbow

15 1 Bracket

16 2 Grommet

17 2 Bushing

18 2 Screw (M6 x 30)

19 4 Washer

20 1 Hose (4-3/4”) Connect to Middle Carburetor

21 1 Auto Enrichner

22 1 Hose, Molded (Bottom) Connect to Lower Manifold Elbow

23 2 Fitting

24 1 Clamp

25 1 Stud (1/4-20 x 1-1/4”) With Dri Loc

26 4 Screw (1/4-20 x 1-1/4”)


Reed Plate, Adaptor Plate and Auto Enrichner - 120 HP1

3

4

5

78

9

10

11

12

13

1415

1617

18

19

20

21

22

23

24

25

1

1

1

15

2

4

6

13


Item Qty. Description Torque

Lb. In. Lb. Ft. N·m

1 4 Clamp

2 1 Hose (2-1/4 in.)

3 1 Fitting

4 2 Clamp

5 1 Hose, Molded

6 1 Hose (2-3/4 in.)

7 1 Gasket

8 4 Reed Plate Assembly

9 1 Plate

10 8 Screw (1/4-20 x 5/8 in.) With Dri Loc

11 1 Gasket

12 1 Adapter Assembly (Upper) Lower Adapter Not Shown

13 14 Screw (1/4-20 x 7/8 in.)

14 2 Screw (M6 x 30)

15 2 Washer

16 2 Bushing

17 2 Grommet

18 1 Bracket

19 2 Screw (1/4-20 x 1-1/4 in.)

20 1 Auto Enrichner

21 4 Nut (3/8-16)

22 4 Stud (3/8-16 x 1-5/8 in.) With Dri Loc

23 2 Gasket

24 1 Stud (1/4-20 x 1 in.) With Dri Loc

25 1 Clamp


Auto EnrichnerSystem DescriptionThe Sport Jet utilizes an automatic enrichner to startthe engine. The auto enrichner is a self contained unitwith three hose connections to allow for 1) fuel inlet,2) air inlet, 3) fuel/air mixture outlet.

Fuel is supplied to the auto enrichner by a hose con-nection to the carburetor float bowl. Air is supplied tothe valve by a hose connection to the sound attenua-tor.

When the engine is cranked a fuel/air mixture isdrawn into the engine from the auto enrichner by ahose connection to the balance tubes. The carburetorshutters must be completely closed for the engine todraw the fuel/air mixture from the auto enrichner.

A wax pellet controls the position of a slide valve andtapered needle. The stator supplies electrical currentto a heater element inside the auto enrichner. As theheater element melts the wax pellet the fuel/air mix-ture is slowly closed off by the slide valve/taperedneedle. The engine continues to run from the fuel/airmixture supplied by the carburetor idle circuit.

a

b

cd

ef

g

h

i j

k

l

m

n

o

a - Stator Leads (Yellow)b - Return Springc - Actuator Rodd - Plastic Spring Guidee - O-ringf - Slide Valveg - Air Inleth - Rubber Seat

i - Fuel Inletj - Tapered Needlek - Fuel/Air Mixture Outlet

(Not All Outlets Are Used)l - Compensating Springm- Brass Guiden - Wax Pelleto - Heater Element

Testing Auto EnrichnerOn a cold engine the tapered needle will move fromfull open to full closed after approximately 2 - 2.5 min-utes of engine running.

On a cold engine resistance between the two yellowleads is 18 - 20 ohms. As the engine warms up the re-sistance reading will approach infinity.

3b fuel system and carburation

Sports